The present invention relates to a pressure pouring furnace, and more particularly to a pouring furnace having a shortened lag time between the issuance of a pouring command and the commencing of pouring, whereby the precision and efficiency of the pouring operation is improved.
Known pressure pouring furnaces comprise a closed molten metal storing chamber having a sprue through to the bottom of the molten metal storing chamber. A pouring chamber connects with the storing chamber via a passage rising upwardly from the bottom of the storing chamber. The pouring chamber has an opening at the top, and a pouring nozzle port in the bottom thereof.
Molten metal stored in the storing chamber is fed to the pouring chamber through the upwardly directed passage by directing air pressure onto the surface of the molten metal through an air pipe provided on the top of the storing chamber.
In these known furnaces the molten metal in the pouring chamber is maintained at a "prelevel", i.e., a level somewhat lower than a height of the bottom of the pouring chamber, corresponding almost to the upper end of the passage connecting the pouring chamber and the storing chamber. To initiate pouring an air pressure, or "shot pressure," is applied to the surface of the molten metal for the period of time corresponding to the quantity of the pour desired, to raise the molten metal level in the pouring chamber to a height over the pouring nozzle port in the bottom of the pouring chamber, thereby pouring the desired quantity through the port into a mold at a given rate.
The disadvantage of these known furnaces is that a lag time of several seconds results after the pouring command is issued in order for the molten metal to rise from the prelevel to the desired level for pouring. Similarly, once the pouring commands terminate, there is still another lag time before the level of molten metal in the pouring chamber recedes and pouring actually ceases. Obviously, these lag times reduce the precision with which the pouring operation is accomplished, and reduce the overall efficiency of the operation. This loss of precision and efficiency is particularly exacerbated in an automated pour work in which these lag times accumulate over repeated pouring operations.